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fbcon: Prevent that screen size is smaller than font size
commit e64242caef
upstream.
We need to prevent that users configure a screen size which is smaller than the
currently selected font size. Otherwise rendering chars on the screen will
access memory outside the graphics memory region.
This patch adds a new function fbcon_modechange_possible() which
implements this check and which later may be extended with other checks
if necessary. The new function is called from the FBIOPUT_VSCREENINFO
ioctl handler in fbmem.c, which will return -EINVAL if userspace asked
for a too small screen size.
Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
b727561ddc
commit
cecb806c76
3 changed files with 35 additions and 1 deletions
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@ -2776,6 +2776,34 @@ void fbcon_update_vcs(struct fb_info *info, bool all)
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}
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EXPORT_SYMBOL(fbcon_update_vcs);
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/* let fbcon check if it supports a new screen resolution */
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int fbcon_modechange_possible(struct fb_info *info, struct fb_var_screeninfo *var)
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{
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struct fbcon_ops *ops = info->fbcon_par;
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struct vc_data *vc;
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unsigned int i;
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WARN_CONSOLE_UNLOCKED();
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if (!ops)
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return 0;
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/* prevent setting a screen size which is smaller than font size */
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for (i = first_fb_vc; i <= last_fb_vc; i++) {
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vc = vc_cons[i].d;
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if (!vc || vc->vc_mode != KD_TEXT ||
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registered_fb[con2fb_map[i]] != info)
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continue;
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if (vc->vc_font.width > FBCON_SWAP(var->rotate, var->xres, var->yres) ||
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vc->vc_font.height > FBCON_SWAP(var->rotate, var->yres, var->xres))
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return -EINVAL;
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(fbcon_modechange_possible);
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int fbcon_mode_deleted(struct fb_info *info,
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struct fb_videomode *mode)
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{
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@ -1119,7 +1119,9 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
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return -EFAULT;
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console_lock();
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lock_fb_info(info);
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ret = fb_set_var(info, &var);
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ret = fbcon_modechange_possible(info, &var);
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if (!ret)
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ret = fb_set_var(info, &var);
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if (!ret)
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fbcon_update_vcs(info, var.activate & FB_ACTIVATE_ALL);
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unlock_fb_info(info);
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@ -15,6 +15,8 @@ void fbcon_new_modelist(struct fb_info *info);
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void fbcon_get_requirement(struct fb_info *info,
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struct fb_blit_caps *caps);
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void fbcon_fb_blanked(struct fb_info *info, int blank);
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int fbcon_modechange_possible(struct fb_info *info,
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struct fb_var_screeninfo *var);
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void fbcon_update_vcs(struct fb_info *info, bool all);
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void fbcon_remap_all(struct fb_info *info);
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int fbcon_set_con2fb_map_ioctl(void __user *argp);
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@ -33,6 +35,8 @@ static inline void fbcon_new_modelist(struct fb_info *info) {}
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static inline void fbcon_get_requirement(struct fb_info *info,
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struct fb_blit_caps *caps) {}
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static inline void fbcon_fb_blanked(struct fb_info *info, int blank) {}
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static inline int fbcon_modechange_possible(struct fb_info *info,
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struct fb_var_screeninfo *var) { return 0; }
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static inline void fbcon_update_vcs(struct fb_info *info, bool all) {}
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static inline void fbcon_remap_all(struct fb_info *info) {}
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static inline int fbcon_set_con2fb_map_ioctl(void __user *argp) { return 0; }
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